The astronomical theory and data compared - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 310

Figure 10.26. The spectrum of Vostok deuterium data according to M&M. Two principal
peaks occur at periods of 100,000 and 41,000 years.
presence of a cycle with a period of roughly 100,000 years. The influence of the
spectral peak at 41,000 years in the time series of Figure 10.25 is less obvious.
There is a very small peak corresponding to 22,000 years.
The results shown in Figure 10.26 create a conundrum. On the one hand, the
presence of strong peaks at periods of 100,000 and 41,000 years suggests that
eccentricity and obliquity are playing predominant roles in determining the
temperature history at Vostok. This should be tempered by the fact that since
some tuning was used to assign the chronology for Vostok data one might expect
that elements of the astronomical model will appear in the spectrum for Vostok
temperatures. On the other hand, the lack of a significant peak corresponding to
22,000 years is disturbing because the variability of solar input to high latitudes
is dominated by precession of the longitude of perihelion. Furthermore, the
spectrum for the variability of Vostok temperature does not resemble the spectrum
for solar input ( Figure 10.24 ) . Whereas eccentricity is the primary peak in the
Vostok spectrum, eccentricity is hardly visible in the solar input spectrum. Thus,
comparison of the frequency spectrum of Vostok ice core data with the frequency
spectrum of solar input to high latitudes provides a mixed result of some overlap,
but significant differences remain. However, if precession of the equinoxes acts
merely as a carrier wave for changes in obliquity and eccentricity, precession
would not affect climate, and the non-appearance of a spectral peak corresponding
to precession would be understandable.
The ice core at EPICA Dome C yielded 800,000 years of data (see Figures
4.10 and 4.12 ) (Jouzel et al., 2007). Spectral analysis of these data was carried out
for two time periods: 0-400 and 400-800 kybp (see Figure 10.27 ) . As was the case